Special Parts

Foekema-Kreidler / 50cc-Racing
Latest update July 4, 2007
Why parts for sale
Because we were asked for it. For some part we are the only one to get these, because they are made by our selves. So if there is some time left, we made these parts also for some enthusiast.

Special parts which are in developping:
- Datalog system, for recording several data of the engine while running. After that, the data can be downloaded in a computer for analysing. This become more and more important for a serious tuner.
- Programble ingnition system, there are many on the market now, but with the knowledge of the UltraSap it was a logical step to make it.
- Gearwheel 33 teeth for 5th gear of a kreidler 5 speed engine, read at the end of this page more about this.

Special Parts available at this moment:
- Exhaust pipe dimensions, based on the characteristics of any 2-stroke engine (20).
- Squish chamber dimensions, incl. degrees instructions for the late (15).
- A combination request for exhaust and combutionchamer is (25).
- Changing aircooled cylinderheads , for using changeable squish chambers(60).
- A new squish chamber for an aircooled cylinderhead (60).
- Watercooled cylinderhead with changeable chambers, for Kreidler VanVeen engine. (400)
- Halffabrics Watercooled cylinderkit for VanVeen Kreidler racer. (230)
- Some halffabric parts for rotary valve inlet, see picture. (75).
- Change your Kreidler engine into a rotary valve one (550).
- UltraSap CDI ignition system, with time delay of 27 degrees,
type I (450) and type II (300) (both excl.coil).
- Change first gear of your Kreidler 5v, dedecated for racing purposes (200)
- 2 gearwheels for the first gear, of a 5 speed kreidler (120).
- Exactly dedicated expansion exhaustpipe only for Kreidler or Puch (230).
- Change Homoet 4P exhaustpipe for 50cc and 60cc (from 85)
Send your questions to 50cc-racing e-mailbox

Aircooled cylinderheads with changeable chambers
Again a developpement which comes out of the racing world. In roadracing changeable chambers are very useal. With differences of only 0,1cc one could tune very accurately the compression ratio on weather conditons and the used fuel. A right squish band and clearence to prevent detonation and to stimulate the speed of burning gas. Even Kreidlers and other twostroke engines for road purpose today are very high tuned and a well calculated chamber might be usefull in that case. The calculation which gives all data about the chamber, also has all the information for the late, like angles, depth, length and diameters. Also the infomation about how to controle the right compression ratio within narrow limits. To let us make a calculation we need some information which you can download here: Fillin form.
Send the information to: 50cc-racing e-mailbox, with the subject "Chamber calculation" and within a few days you get all the data to make the best chamber you can get.

Exhaustpipe Calculations
The exhaustpipe is without any doubt one of the most important parts by tuning a twostroke engine to the limit. You might have done everything like fast cylinders and enough compression and a big carburettor and still it does not work well, mostly because your exhaustpipe is not well calculated. In all the corresponding with many enthousiasts it happens many times that it is all about tuning and most of them about the exhaustpipe. So finally we decided to setup a service for calculation of exhaust dimensions for twostroke engine. The first year we got more and more requests, so we have to stop this service for free. Send the form (below) with your properties as an attachment to the 50cc-racing e-mailbox. Within a few days you get back the measurements of the most dedicated exhaustpipe you might have, in lenght and diametres of 7 parts and the templates, including usefull information how to made it as easy as possible.
The exhaust calculation is of course just one part of the total tuning aspects,but for most beginning tuners one of the most difficult parts. The chapter about tuning that will starts soon, will help you by many other details which are more or less important.
Read the special Expansion exhaust page
Or fill in the form to request exhaust dimensions. and mail it to: 50cc-racing e-mailbox with subject "Exhaust dimensions"

Tuning the Gearbox for Racing
To change a quantity produced Kreidler 5 speed gearbox into a racing gearbox, it is absolutely necessary to change the first gear. Most 50cc racing events today are done on short circuits like karting, and bicycle circuits. Therefore you need a firstgear of about 40% of the topspeed. The first gear of a Kreidler 4 speed is already 40%, so nothing has to be changed. For the 5 speed the standard 1th gear is 31-32%, which is far to low, and even dangerous when shifting in the first gear in low speed corners were about 40% is needed. So a new set of gearwheels is available to achieve that 40%. After changing the first gear and still looking to make it more better, you may even change the 5th gear. The standard 5th gearwheel on the second shaft has 31 or 32 teeth, unless both are suitable, a 33 teeth would be more desirable. The last shifting from 4th to 5th gear should be at best between 9-10% on short circuits. 31 teeth results in 15,3%, 32 teeth in 12,6% and 33 teeth in 9,9%.

Kreidler 5 speed models and modifications for racing:
31-53-71-85-100 = 5 speed Kreidler standard (5th with 31 teeth)
32-54-73-87-100 = 5 speed Kreidler standard (5th with 32 teeth)
33-56-75-90-100 = 5 speed Kreidler 5th modified with 33 teeth
39-54-73-87-100 = 5 speed Kreidler 1th modified with 15:44 teethwheels
40-56-75-90-100 = 5 speed Kreidler 1th and 5th modified
43-61-76-91-100 = 5 speed Kreidler VanVeen racer 1967

Kreidler 4 speed gearbox:
40-65-81-100 = 4 speed Kreidler standard

For comparing some gearboxes more:
46-61-73-84-94-100 = 6 speed Kreidler R77 GP racer
41-57-70-82-93-100 = 6 speed Kreidler Schaftleitner GP racer
37-54-70-82-92-100 = 6 speed Kreidler Crossing
28-43-59-78-88-100 = 6 speed Honda NSR standard
53-66-77-86-93-100 = 6 speed 125cc Honda GP racer 2004
48-59-73-86-100 = 5 speed 250cc Yamaha Crossing 1991

Look also the graphics in the Excelfile to see the differences.
So download the Excel file.

Information about tuning
Exhaust chambers
Combution chambers
Inlet systems
Rotary valve
Kreidler 6V racing engine

UltraSap CDI with timedelay, (type I =450)

Cylinderhead with changeable squish chambers

Changeable chambers for an aircooled cylinderhead (60)

Chambers dimension calculation (15)

Cylinderhead for Kreidler vanVeen engine (400)

Halffabrics cylinderunit for Kreidler vanVeen engine (230)

Halffabrics set for a rotery valve inlet system (75)

Kreidler gearwheels for the first gear, to made a real 5 speed racing gearbox (120)

Kreidler RS cylinder tuned by Luc, he was in 1968 the fastest private driver with 168 km/h at TT Assen.

If the English version is not ready, you will be automaticle passed to the Dutch version
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